Figure 1.

The study design

First, we compared the sleep status (sleep variables and sleep quality) and HRQOL between morning and evening types. Second, we compared the sleep status and HRQOL between early working condition (the working style involved pre-determined working hours from 09:00 to 17:15 hrs, recommended early morning work from 05:00 to 08:00 hrs, and a prohibition of overtime work after 20:00 hrs) and normal working condition (the working style involved pre-determined working hours from 09:15 to 17:30 hrs, from 09:00 to 17:30 hrs or from 09:00 to 17:45 hrs and permitted overtime work after 20:00 hrs) in each chronotype.

MEQ, the Morningness-Eveningness Questionnaire; HRQOL, health related quality of life.